Hello World!

Topics: logging, app, run

Lets get started with a simple message box. Source.

extern crate kas;
use kas::widgets::dialog::MessageBox;

fn main() -> kas::app::Result<()> {
    env_logger::init();

    let window = MessageBox::new("Message").into_window("Hello world");

    kas::app::Default::new(())?.with(window).run()
}

cargo run --example hello

Logging

Enabling a logger is optional, but can be very useful for debugging:

#![allow(unused)]
fn main() {
env_logger::init();
}

Kas uses the log facade internally. To see the output, we need an implementation, such as env_logger.

Trace level can be a bit chatty; to get a reasonable level of output you might try this:

export RUST_LOG=warn,naga=error,kas=debug
cargo run --example hello

A window, a shell

Next, we construct a MessageBox widget, then wrap with a Window:

#![allow(unused)]
fn main() {
extern crate kas;
use kas::widgets::dialog::MessageBox;
let window = MessageBox::new("Message")
    .into_window("Hello world");
let _: kas::Window<()> = window;
}

Finally, we construct a default app, add this window, and run:

extern crate kas;
use kas::widgets::dialog::MessageBox;
fn main() -> kas::app::Result<()> {
let window = MessageBox::new("Message").into_window("Hello world");
kas::app::Default::new(())?
    .with(window)
    .run()
}

kas::app::Default is just a parameterisation of kas::app::Application which selects a sensible graphics backend and theme.

If you wanted to select your own theme instead, you could do so as follows:

extern crate kas;
use kas::widgets::dialog::MessageBox;
fn main() -> kas::app::Result<()> {
let window = MessageBox::new("Message").into_window("Hello world");
let theme = kas::theme::SimpleTheme::new();
kas::app::Default::with_theme(theme)
    .build(())?
    .with(window)
    .run()
}

Or, if you wanted to specify the graphics backend and theme:

extern crate kas;
use kas::widgets::dialog::MessageBox;
fn main() -> kas::app::Result<()> {
let window = MessageBox::new("Message").into_window("Hello world");
kas_wgpu::WgpuBuilder::new(())
    .with_theme(kas_wgpu::ShadedTheme::new())
    .build(())?
    .with(window)
    .run()
}

Finally, Application::run starts our UI. This method runs the event-loop internally, returning Ok(()) once all windows have closed successfully.